The United States is concerned that the Taiwanese don't have enough to deter a Chinese invasion.
Sometimes I read that the Taiwanese will fight tooth and nail. Other times I read that the Taiwanese have critical weaknesses that make their fighting ability less than it appears. I guess this is the latter type of thing:
U.S. officials, former Taiwanese military leaders and security experts say they believe that means Taiwan needs to do more to ensure it can inflict enough damage to discourage an invading force or hold it off until the arrival of help—possibly from the U.S. After years of increases in military spending, China now has around 100 times as many ground force personnel as Taiwan and a military budget 25 times as large, according to Pentagon data.
As I've noted before, Taiwan needs to focus on spending more before it gets into the details of spending smarter. Virtually any increased spending anywhere will help at this point. Because Taiwan needs to fight on so many domains to have a chance at winning.
Note that the reference to "guerrilla-style" warfare in the article really means "asymmetric" means of fighting. That is you don't try to match an enemy destroyer for destroyer or fighter plane for fighter plane.
Which is a valid if mis-used concept.
And not to sound threatening rather than cautionary, but America can make up for only so many Taiwanese deficiencies.
The Chinese communists on the mainland naturally think that is badthink and worthy of punishment or invasion.