which weapons were better in the second war: the American or the German?

The American army with the English.

I think it’s a myth to say either side had “better” weapons. The Germans certainly had some good ( I know weapons aren’t good in any sense but let me use the word as short for advanced/ effective / well engineered etc), weapons especially their tanks and advanced jet planes and rocket technology., but so did other countries.

Britain was advanced in aircraft ( they had operational jets before the end), and conventional navy , USA and Japan were advance in aircraft carriers and the aircraft to go with them, and Russia’s tanks were nearly as good as the Germans .

So each had an advantage somewhere but USA ( and Russia to some extent) excelled at mass production, and could replace their equipment and supply their allies far faster than the axis could . So while the Sherman tank may not have been as technically good as a Tiger, if it outnumbered it sufficiently, it was going to win.

Depends on what you mean by weapons, and also about what you mean by better.  

For example, the Luftwaffe fielded jet and rocket fighters which were much faster than any US (or other Allied) aircraft, but which were terribly difficult to maintain, and which were not able to change the course of the war when they went up against American and British piston-driven fighters.   The Wehrmacht fielded some advanced, powerful tank designs, from the Mk V Leopard to the Tiger and King Tiger models.  These had thick armor and very powerful guns, and were almost impervious to the guns American tanks used.  However, the M-4 Sherman was lighter, faster, much easier to maintain, much more reliable, and eight of them could be produced in the time it took the Germans to produce a single King Tiger.  The STG-44 was the first widely fielded assault rifle, and was excellent, but it was fairly difficult and expensive to produce (which is why the Germans continued looking towards a "Volks Sturm Gewehr" which would be simpler and cheaper.  In comparison with American small arms, the STG was better in some ways, but again, because of its cost and complexity, it was produced and fielded in small numbers, while the M-1 Garand, M-1 Carbine, BAR and M-3 Grease Gun were able to be produced in very large numbers, and were simpler to maintain.  

What about English weapons like the dam buster bombs? What about Japanese weapons? Chinese weapons?

Though the atom bomb sort of trumps them all, it was not used on Germany by the US.

Also, the European war was mostly Russia and England vs. Germany. The US only entered late, and quite reluctantly.

Both had weapons that were better and subject to improvement during the war that made them that way. You're seeking opinion. Germany never deployed an aircraft carrier in WW2 as an example how far behind Germany was in one aspect of weaponry. The US also had the proximity fuse and Norden bomb site which were other huge advantages.

German weapons obviously weren't good enough as the Americans destroyed Germany. 

that would be German most hand Guns made By Germany were Better the Only tank made by the Germans that Failed was the Tiger

the Sherman had only two Good Points easy to repair and easy to make

the Americans never had a Decent Fighter until they got the RR Mustang

In the end Germany Lost WW2 because they ran out of Fuel

German. German weapons like the MP40, StG 44, and FG 42 heavily influenced future weapons from multiple countries. The Kar 98k was a bolt action rifle that is praised for accuracy and range. Artillery such as the Flak 88 also proved very effective. The V1 and V2 rockets speak for themselves.