The US doesn't need two months, they can send one Supercarrier and two amphibious ships with F-35s within a day. Flying more planes to Japan won't take very long either. The political process in the US is slow and American forces will probably wait for resupplies to be organised before joining the war, so there might be two weeks of time before they intervene. Assuming of course that they're determined to take part in the war.
China won't have the luxury of time, initial landings have to happen as soon as possible. The outlying islands and penghu should be taken in the first two days followed by landings on the main island. The ROC forces may or may not surrender, but giving them time only allows political pressure in the US to build up, ensuring that a US China war happens. You also can't give them two months to train reservists.
And where exactly are those ships coming from? Even the think tanks are admitting that China is likely to wipe out the carrier group and air bases stationed in Asia in a surprise attack. The entire point of staging large scale war games instead of multi months build up is to normalize these operations and leave US/Japanese military as unprepared as possible. That's why US military is getting so alarmed about the entire situation. The working assumption is that China will throw everything at the 7th fleet and JSDF in that initial attack and wiping out everything inside 2nd island chain.
After this initial attack, US military will be looking to see which aircraft carriers can be surged in the next 30 days, bring them to west coast or Pearl and prepare for a long mission. US Navy is never going to be bringing just 1 or 2 carriers over. It will need to bring at least 3 and possibly 4 carriers over. According to patchwork, anything more than that, US Navy would not have replenishment ships needed to actually support this large fleet. And, it will take US military 2 months to be fully ready to bring over such a large strike group. If you are PLA, you will spend this time trying to make sure that this large flotilla does not get support from anywhere else. As in, you use your dominance of SCS to make sure that all the ASEAN nations fall in line and for Japan to never allow US military in those bases again. Fall in line means that these countries do not side with America for rest of the conflict and to allow Chinese missiles/aircraft flyover rights. The way to do that is aggressively utilize 056s and cutters to patrol SCS and ECS so that only countries that fall in line can continue trading with rest of the world. In certain cases like Myanmar and Cambodia, to be given the rights to basing your aircraft, ships and missiles there.
If PLA's lesson from Ukraine conflict is that China needs to be fully prepared for a full fledged war scenario, then it will need to build up enough of a force to:
1) take out all US/Japanese forces west of Pearl Harbor in that initial attack + keeping the bases non functional for the duration of the conflict
2) be able to fully blockade Taiwan and control trading/energy routes that all the East and Southeast Asian countries depend on
3) defeating the large strike force that US military will inevitably send over
To me, we will see an even more accelerated pace of purchase on the long range missiles, precision missiles, surface combatants, aircraft, helicopters and drones.