Immigration puts an unnecessary strain on already overwhelmed public services, particularly in countries with free healthcare, like the UK. It increases the tension on already stretched resources. Many immigrants will spend time on social welfare whilst looking for work which is expensive to the taxpayer.  These services are reserved for tax-paying citizens. Many countries are already overcrowded and cannot easily produce extra housing to accommodate an influx of people. This consideration is particularly true of social housing, of which there is limited space. Additionally, public roads become crowded and create gridlock, while trains and buses are overwhelmed. Extra people also create extra competition for school places and hospital beds. There will not be enough doctors or dentists per head of population if migrants are allowed in. We do not have the infrastructure to support an untold number of migrants. Immigrants are costly in terms of taxation and put stress on local infrastructure. Countries would be better off not accepting immigrants.
Immigrants do not put a strain on public services because they contribute tax money as well as receiving tax benefits. As the number of people grows, the tax revenue grows. Many immigrants are net contributors to the economy because, having moved in adulthood, they have not used costly educational services. Studies have found that immigrants are less likely to use welfare benefits than native citizens. Immigrants are a boon to infrastructure because they contribute to the skills gap by providing doctors, nurses, and other needed professionals, of which we do not have enough. Unscrupulous politicians who underfund public infrastructure frequently and unfairly lay the blame on immigrants. Poor public services are caused by persistent neglect and refusal to pay for them with higher taxes. Immigration does not necessarily cause overcrowding; it's poor planning and a lack of funding that contributes to overcrowding. Immigration allows in people who can be net contributors to the economy and provide much-needed skills.
[P1] Immigrants cost the taxpayer money due to their use of social welfare and healthcare. [P2] Immigration puts considerable strain on limited infrastructure. [C] Immigration overwhelms public services and should be stopped.
Rejecting the premises
[Rejecting P1] Immigrants contribute more than they receive in taxes. [Rejecting P2] Immigrants contribute skills and tax revenue to existing infrastructure.