> Currency in practice is our measure of capital, but it isn't inherently capital.
In fact it is the only real capital that exists. The rest is just leverage. In a real economy all debts must be settled with sovereign debt ie currency.
> The government could give everyone a trillion dollars, but whoever actually owns land and factories and natural resources will still be the people with capital.
You've fallen to our own confusion. This is the classic mistake of people who don't understand Marx: the mere presence of assets doesn't make you a capitalist. Everybody has assets. It is only the people with currency (more precisely, the people owed currency) that are capitalists because their assets are sovereign liabilities and therefore must be accepted for all debt settlements. The "inside economy" can actually grow as long as people accept the sovereign debt for payments. The only limit of this process are the sovereign's borders and the existence of foreigners who refuse to be paid with the sovereign debt.
This is important, particularly if you want to understand what's actually happening in China, where the entire system is driven by massive amounts of sovereign debt but the country as a whole has zero external debts (including its external assets). Growth, as the last forty years of China's history makes very clear, is not limited by any kind of exogenous investment. Countries don't need to borrow money to grow despite the narrative pushed by the global bankers.