Why does the USA celebrate Thanks giving  when the British founded them only to celebrate Independence Day?

Not exactly, no chance. The Pilgrims came to the New World for freedom to practice their religion. They were damned if they were going to permit the practice of any other religion. In fact, it might be said that the Pilgrims came here because they lacked the power to force their religion on everyone else.

Columbus wasn't British and he didn't FOUND America. 

Thanksgiving was celebrated to honor the pilgrims' survival over a very hard year. Independence Day was begun to celebrate the United States' break from British rule. 

Read a history book, dear. It doesn't matter if you're British or not--wherever you got these facts must have been a comic book. 

Thanksgiving was a celebration of the Pilgrims first bountiful harvest (giving thanks to God) in the New World with the help of their Indian neighbors in the 1600's. It has nothing to do with any future independence Day celebration. Thanksgiving has turned into a celebration of family and giving thanks (to God) and counting your blessings.

While the British set up the Colonies. As the years went by the Colonists grew more and more upset with how they were treated by the Crown, until they had enough and declared their independence from Britain on July 4 (technically July 2) 1776.

So many errors it was hard to get the meaning of your question. Columbus was not the founder of America, America had already been discovered when he reached her shores.  Thanksgiving is for giving thanks this is why it is in the fall after the harvest.  Independence day reflects freedom from other countries from which the colonist were anxious to leave due to oppression from European countries like England, Spain, France. Once the decleration of independence was signed and the Colonies were joined together the United States of America became a union of colonies and were accorded self governance after the British and French and Spaniards were defeated.  Independence day is July 4, one is in summer one in the fall.  My history may be off a little but both days are important to the foundations of America. 

Boo-Bottle, you must be making a poor joke.

Any Briton knows Christopher Columbus was a sailor from Genoa and was backed by Ferdinand of Aragon and Isabella of Castile. John and Sebastián Cabot were his fellow countrymen and were backed by Henry VII of England a decade later. 

You know about harvest festivals too because they are as old as ancient Britain. After the farmers reaped their harvests and stored them, they had feasts for their workers - the villagers thanking God or gods for food to feed themselves throughout winter. 

Columbus never held a harvest festival in the New World. The Pilgrims at Massachusetts - not the inhabitants of Roanoke or Jamestown Virginia - held the Thanksgiving feast that is commemorated in the US today.

Columbus Day in the US usually occurs on the same day as Canada's Thanksgiving Day - the second Monday in October. (You had heard of Canada, eh? It's that block of former British territory between the United States and the North Pole. It should be mentioned in British history books since so many of its military personnel fought for Britain and the British Empire.) I doubt there is any connection to Martin Frobisher's voyage because no Canadian mentions him or it in regard to Thanksgiving. (Though I am sure Martin and crew were grateful to be alive and, if they were in the Arctic in October, very earnest in praying the ice would not close off their ship from the open sea.) It is a harvest festival, like harvest festivals in other countries. Churches are decorated with food produce. Thanksgiving worship services are celebrated on Sunday and we feast on  Sunday evening and have a bank holiday on Monday. 

The celebration of the signing of the Declaration of Independence every July 4 is a different holiday, for the reason in its name. "We have broken our ties with Britain and won't return to her rule  We are Americans now " Aside from eating and drinking, it does not resemble Thanksgiving Day.

COLUMBUS WAS NOT BRITISH HE WAS ITALIAN. YOU NEED TO READ HISTORY.ARE WE TALKING . SO YOU ARE BRITISH YOU NEED TO KNOW THAT CRISTOBAL COLUMBUS.WAS NEVER BRITISH. I WILL FORGIVE YOUR IGNORANCE.AND ABOUT THANK GIVING. I DO NOT KNOW WERE THAT CAME FROM. BACK THEN  I DON'T THINK THEY HAD BUTTERBALLS TURKEYS.

I'M ALSO A LITTLE OGNORANT BUT I WILL GUGLE AND FIND OUT.

You lost me w/ "Columbus was British".

It is surprising someone British would not know Columbus was Italian and was sailing under the flag of Spain when he discovered america. Queen Isabella sponsored Christopher Columbus to find a better route to the far east and he bumped into north america on one of the Caribbean Islands.

The British gave us nothing. The pilgrims fled Britan to find religious freedom

cause they like to celebrate both