Amendments require approval of 3/4 of states and there are still enough states to vote against. Also what amendment, specifically? That Trump can be president more times? Exert more power? Eliminate opposing political parties? Legislate pi to be 3?
Why go through all the trouble of amending the Constitution when you can just do whatever you want because nobody's going to stop you? Suppose Trump declared himself king tomorrow. Who with any power is going to push back? It doesn't matter if it's against the law if nobody cares about the law.
