Chinese planners expect that the earliest landing forces that do reach Taiwanese soil will have to fight without effective air-ground support. This is where Taiwan knows it can win: by using highly mobile forces to isolate and annihilate pockets of landing troops. While China would use its mainland missile forces to wreak havoc on fixed Taiwanese positions such as air bases and depots, it would struggle to target mobile Taiwanese forces. That's where these new tanks and stingers come in. And if the Chinese advance force can't get off the beaches, well, China has a big problem.
I am fully on board the idea that Taiwan will need to counter-attack Chinese bridge- and air-heads:
I don’t believe a crust defense can stop China off of Taiwan. Sizable forces will make it ashore through any gauntlet given the overwhelming Chinese naval, air, and economic advantage. Combined with the ability to choose the timing of invasion, Taiwan must defend in depth.
And if Taiwan’s ground forces can’t quickly crush the bridgeheads and airheads before the PLA gets organized, China will defeat Taiwan and crush their island democracy.
Although as that first link in my quote explains in some detail, I don't think a Chinese invasion will come across the beaches in a replay of D-Day.
UPDATE: I'm not sure why this Chinese reaction is a problem--why would any American company sell weapons to China too?