None of us were born in the 1800's or 1920-30 ( vince and wes excluded) so my point of view is not based on then. Yes little areas assembled back then, little Italy, china, etc... But I'm talking about the last dozen or so years.
http://www.manhattan-institute.org/html/cr_76.htm#.Uo-F_uKmamQAssimilation at its highest level in decadesFigure 2 displays the long-term trends in the assimilation index from 1980 to 2011. The figure shows trends in the composite assimilation index, which incorporates data on economic, civic, and cultural indicators, and component indices that consider sets of indicators in isolation. The composite index is always lower than the components. Logically, the algorithm used to predict whether an individual is native- or foreign-born is always more effective when it uses more information. The composite index uses the most information.
All measures, the composite and all components, have shown an increase in recent years. These trends are most obvious using cultural and civic indicators. Since the onset of recession, these two indices have increased steadily. The economic assimilation index, by contrast, fell during the recession, underscoring the particular vulnerability of immigrant families in the American economy. Economic assimilation shows an uptick, however, in the most recent data. The composite index now stands at 30, after spending more than two decades in the 20s.
All four measures now stand at levels that have not been exceeded since the 1980s. The degree of similarity between the foreign- and native-born populations is now higher than it has been in a generation.