Is it time for Americans to cause amendments to their Constitution so that a defeated candidate will not be allowed to continue in power?

We already did that.  Before 1932, the winning candidates did not take office until March.  Now Congress takes office on January 3 and the President takes office on January 20.

That is really as fast as it can be done.  For a variety of reasons, it takes several weeks after the election to finish the count and certify the results.  Federal law gives states a deadline of December 8 (this year) to finish the count.  The electoral college then meets to officially vote the following week (December 14 this year).  Since Congress should be adjourned by that point, Congress can't certify the electoral college vote until early January.  And there is the theoretical possibility that Congress would have to select the winner if nobody gets a majority of the vote.  In short, January 20 is probably the earliest that the new president can take over.

Unfortunately, because, in most elections, it is clear who won before the last vote has been counted and before local election authorities do the checks to make sure that everything was counted properly, that you have an "apparent winner" and an "apparent loser" long before you have an official winner and an official loser. However, every election is different and, on rare occasions, you have an election close enough that you need to count every vote to determine who won and the checks reveal a mistake that alters the results.  So to allow the process time to work out, there will be a gap between when we have an apparent winner and an official winner.  We just need checks on what a president and Congress can due during a "lame duck" period.  

Sorry Snowflake ! You've been played the f00l !

On Nov 13, 2020 Jody Hice wrote Jill Murphy a letter saying The DNC lied and there is no President Elect !

Trump is the only one trying to follow the US Constitution, and being honest !

Yet look what the Propaganda has  you believing !

These loopholes should be corrected so it will not happen again.  

Yes because that would be 2 wrongs don't make America greater, trump will win, and if it takes the courts a little longer to declare him winner , so be it, the left knows they  themselves  have cheated

No.  We don't make amendments easily to our Constitution.  That is the greatest document ever written and it stands by itself.  We have proven voter fraud of machines changing votes.  See if such nonsense were in the Constitution the American people would lose a great right.

That's not a "loophole", it's a feature. Amending the Constitution to address one man in one specific situation would be like using a nuclear tipped ICBM to swat a fly. 

No need. At noon on 20 January, he can be removed as a trespasser, if need be. At that point, the IRS and NYS Dept. of Revenue get their shots at him.

This question is moot.  Even if we accept the apparent election results...Trump was elected for 4 years.  (not 3 and a half)  Biden doesn't assume power immediately at the end of the vote counting.  Trump has done absolutely nothing wrong.  If he left office now, he would be literally AWOL.

A Constitutional Convention is long overdue, there are many issues that need to be addressed.