There seems to be a failure to understand cost and benefit here. Myanmar, currently not hostile, presents a situation where the advantages of invading (in whole or in parts), turning it hostile, and subsequently having to address and resolve such hostilities outweigh the challenges of reunifying Taiwan. Taiwan, already harboring hostility, seeks American weapons and support, posing a threat to sovereignty. It's essentially a matter of removing an existing enemy versus creating more, a very basic calculation.