Warren's plan was to sell to exporting nations import credits (ICs) that are less fundamental than national bonds, and that diminish intergenerational unfairness from foreign real estate holdings. The proposal sounds like a gentle version of capital controls or outright bans on foreign land ownership, which US trading partners implemented.

The irony of course is that Warren is a leader of the very business community that struck this Faustian bargain, and he probably accumulated a fair quantity of land and bonds through exactly this process. He's basically pleading with politicians to change the math so he can make money a way that is better for the nation.