The federal government has mandated a federal minimum wage of $7.25/hour, which seems like a ridiculously low number for any one person to try to make some sort of living from, but even that minimum wage has exceptions made to it so that certain professions in certain States are permitted to lower the minimum wage to even less than $3/hour if that person, for example, is a server in a restaurant, of which, the belief is that their income will not come from their wages, per se, but from the tips of the consumers. In addition, States are permitted to raise the minimum wage above the Federal level within their State, of which 29 States have done so.
While it is true that $15/hour does not go as far in certain areas of the country, that represent a high cost of living, such as New York City or San Francisco; there are other cities such as Buffalo and Kansas City in which the cost of living is very reasonable, but be that as it may, $15/hour, in a country in which, people are permitted to move from high cost of living cities to lower cost of living cities or wherever they so desire to move to, in addition to the fact that States and cities have the option to help subsidy those that reside within their State or city, $15/hour is probably considered to be a wage that is high enough that most people can make a fair living from it, in one way or another.
As reported by oxfarmarmerica.org, "Overall, 58.3 million workers (43.7 percent) earn under $15 an hour; 41.7 million (31.3 percent) earn under $12 an hour." That represents not only a staggering percentage of Americans that do not make$15/hour but also represents a staggering amount of working Americans in total that do not make $15/hour, and while people may protest and fight for a nationwide increase in wages to $15/hour of which the burden for paying those wages would rest upon the businesses that currently do not pay those wages, there is another way to basically accomplish the same goal.
While it is difficult to calculate exactly how many billions would be needed for the Federal Government to provide on a biweekly basis, a direct subsidy to all those that are working, but making less than $15/hour, it can be calculated using a "back of the envelop" basis as follows: that it is estimated that on average 58.3 million workers are making $10/hr, so the Federal Government would need to make up that $5/hr, multiplied by eight hours in a day, then multiplied by fifty weeks in the year, and finally multiplied by 58.3 million workers, which would equate to a total of $583 billion. While that number is indeed staggering, it could be mitigated by the following: Earn Income Tax Credit (EITC) for 2017 was $65 billion, and this would be reduced considerably; further, as reported by wikipedia.org, "Roughly half of this welfare assistance, or $462 billion went to families with children," which would also be reduced considerably, and further not all of those 58.3 million workers are actually working a forty hour week. In addition, this Federal Government, for FY 2019, is scheduled to have a deficit of about $1 trillion, and yet, this government still stands, so adding another $350-500 billion to it, would not collapse said government.
Finally, unlike a lot of other government programs, which are purposeless, pointless, chaotic, and inefficient--a program that subsidizes incomes in America, would go directly into the very hands of people that will, more times than not, spend it on personal consumption within the United States, of which, more personal consumption, equates to a higher GDP, and will, therefore, help make America great, again.