Yes if a president withholds funds Congress appropriated he can be impeached. It was the basis of the first impeachment of Trump for withholding aid to Ukraine in 2019.
It applies to every president. It is part of the Impoundment Control Act of 1974 after Nixon blocked appropriated funds.
It isn't an impeachment time bomb. Trump just needs to follow the law. The president doesn't have the power of the purse. Congress does. Trump can't unilaterally block Ukraine aid.