Yes, Roosevelt's New Deal created modern America, both politically and economically. Up until this time, social welfare, as it was, was handled by state governments. The federal government prior to the 1930s did not define its role as including helping Americans prosper economically or providing a safety net in times of distress. The crisis of the Great Depression, however, was so massive that FDR's government was willing to try what were then considered radical experiments in social welfare. For the first time, federal programs were enacted, such as Social Security, jobs programs, low-cost mortgages, and mortgage refinancing to help people avoid foreclosure. Rather than a patchwork of state solutions, these programs provided an umbrella for all Americans—at least all white Americans. The New Deal also established the 40-hour work week and a federal minimum wage, and it banned child labor. In other words, it was the beginning of the social order as we know it today. Much that we take for granted simply did not exist before the New Deal.

Because of these many programs, after World War II, a huge middle class was able to emerge in the United States. People could buy their homes with stable mortgages, earn decent wages, work decent hours, and know they would get Social Security and not starve in old age. People also knew the government had safety nets in place, so that if a crisis occurred, resources were available to tide them through. Life no longer had to be lived in fear. People were able to accumulate wealth. Young people could finish high school and go to college because there was no pressing need for them to start earning money at 14, 15, or 16. People had money to spend, and this in turn led to greater economic growth, in what is known as a virtuous cycle.

I would agree that Roosevelt's New Deal was the beginning of our Modern Day economic system. The New Deal was the beginning of lots of government interaction in the economy of the country. I am not so sure that the New Deal was the beginning of our current political system.

F.D.R.'s New Deal was a massively important step in the creation of modern America, both politically and economically.  However, the founding fathers of modern America both politically and economically, were Abraham Lincoln, Thaddeus Stevens, Charles Sumner, Lewis and Arthur Tappan, and others.

An article illustrating this, is:

Current, Richard Nelson. "Love, Hate and Thaddeus Stevens," Arguing with Historians: Essays on the Historical and the Unhistorical (1963), 83-96.

I agree with this statement.  The New Deal was the beginning of the political and economic system we have today.  The New Deal started us on the road to the system we have now where government and the economy are intertwined and where politics is largely based on what Lowi would call "interest group liberalism."

Before the New Deal, the government kept (mostly) out of the economy.  It did not try to do things like building dams or irrigation projects or encouraging farmers to leave their fields fallow.  With the New Deal, this changed.

With the New Deal, there also came the idea that governing is about keeping each interest group happy (usually by buying it off).  This is not to say that government wasn't worried about keeping various interest groups happy before, but since the New Deal, this has become a much larger part of how government works.  We have a system now where economic policy seems to be a process of the government giving various groups what they want in terms of tax breaks and subsidies.