The US is going to lose to China with this no matter what. There is no way we can compete with three carriers that are owned and financed by the Chinese government using the equipment of companies that are also under the control of the Chinese government, with all three of the mobile carriers also having direct access to the country's fiber backbone, again by order the government, all without the permitting issues the US has because the Chinese government has prioritized deployment of 5G in their national economic plan and there's no such thing as NIMBYs in China. Not to mention spectrum isn't bought in China, it's allocated as a resource for the good the country's economic interest, such as that it's designed for optimal deployments in LTE and now 5G (it's being reconfigured). That type of synergy is unimaginable in the US.
This is without mentioning the fact that the government has consolidated the towers of China Telecom and China Unicom (the two smaller carriers in China) into China Tower (again, owned by the Chinese government) so that they basically share towers and are sharing the burden of 5G deployment. China Mobile has a network that was built with a density and spacing that was optimized for Band 41 LTE, which means they alone have more than 1,000,000 deployed cell sites, and they are being reallocated additional 2500/2600mhz spectrum from China Unicom and China Telecom for 5G - they'll just have to add equipment to existing towers which are already spaced with appropriate density. Oh, and the entirety of China's 700mhz spectrum in the APT TDD allocation (band 44, equivalent to bands 12/13/14/29 in the US) will also likely be used for 5G when that spectrum is cleared in a few years. Where US carriers add spectrum to avoid the cost of increasing density, Chinese carriers increase density to make better use of spectrum resources, meaning more bandwidth for 5G while keeping LTE performance. China Unicom and Telecom have been allocated the IMT spectrum in the 3.5ghz band that will be the international standard. A huge amount of the Chinese economy is built around smartphones, mobile payments, the gig economy, etc. - much more than in the US, and it's a massive government priority - T-Mobile combining with Sprint will have a minimal comparative effect on the ability of the US to "win" in the race to 5G considering all of these factors. They are basically bamboozling people who don't know better with what is basically an appeal to economic nationalism.