Invest is a useful euphemism. It means spend, of course, but implies something more. Spending with a purpose, with a higher expectation. "We're going to spend two billion dollars on more state stimulus." No good. "We're going to invest two billion in American infrastructure and our children." Now we're talking.
The distinction between investing and spending is often rhetorical, but not always. All spending is not equal. Compare Social Security with infrastructure. Social Security pays seniors a monthly check to preserve their lifestyle through retirement. The program is crucial, but it's hard to call it an investment (unless you're bold enough to say it invests in aggregate demand). It's designed to preserve, not pay off. Infrastructure spending, on the other hand, is absolutely an investment. Roads carry people and cargo, free up traffic, and increase productivity. Each dollar spent on new infrastructure pays off in the work in facilitates.
In the 1950s, we built roads. Infrastructure spending was eight times its current level, as a percentage of GDP. Today, we preserve retirement. Medicare, Medicaid, Social Security and other pensions will make up almost half the federal budget in 2020. The U.S. spends $4 on elderly people for every $1 it spends on those under 18.